共查询到20条相似文献，搜索用时 22 毫秒
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Simhadri Ravishankar;M. D. Selvaraj; 《International Journal of Communication Systems》2024,37(16):e5905
The future wireless communication networks (beyond 5G) are intended to provide seamless connectivity, higher data rates, and lower latency. The intelligent reflecting surface (IRS) promises extended network coverage. The non-orthogonal multiple access (NOMA) technique provides higher spectral efficiency and supports a larger number of users. In general, the cell-edge users far from the base station are affected by severe fading, which may result in an outage. To overcome this issue, we propose an IRS-aided device-to-device (D2D)-enabled two cells coordinated NOMA system in which a common cell-edge user acts as D2D receiver. The cell-edge user receives the signals from near users, IRSs, and both base stations to achieve better diversity. We analyze the outage probability of cell-edge user, while all the fading channels are assumed Nakagami- and obtain a closed-form expression at higher signal-to-noise ratios. We develop an algorithm to find the ergodic capacity of the cell-edge user. We validate the mathematical expressions with simulation results and see a substantial improvement in outage performance over the existing systems. 相似文献
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转接节点的选择是协作通信中的一个比较重要的问题.在许多实际情况中并不是所有节点都参与转接,本文研究了在所有潜在的转接节点中任选一个节点作为转接节点的协作分集方法,推导了这种协作分集方法中断概率的上界和下界.理论计算和仿真结果表明该协作分集的 中断概率的上界基本不随潜在的转接节点的数目的增加而变化,而下界却随潜在的转接节点的数目的增加而显著降低. 相似文献
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Hakan A. Cirpan Osman N. Ucan 《International Journal of Satellite Communications and Networking》2001,19(2):159-168
In this paper, a blind maximum‐likelihood channel estimation algorithm is developed for quadrature partial response‐trellis coded modulated (QPR‐TCM) signals propagating through a Rician fading environment. A hidden Markov model (HMM) formulation of the problem is introduced and the Baum–Welch parameter estimation algorithm is modified to provide a computationally efficient solution to the resulting optimization problem. Performance analysis of the proposed method is carried out through the evaluation of bit‐error probability upper bound for Rician fading channels. Also, some illustrative simulations are presented. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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Md Fazlul Kader 《International Journal of Electronics》2013,100(6):1050-1062
Non-orthogonal multiple access (NOMA) has attracted a significant attention to the research community as a potential candidate for 5G or future radio access. This article presents a NOMA-based cooperative network where a transmitter considered as a base station communicates simultaneously with two users treating as a far user and a near user via the help of a half-duplex decode-and-forward relay. We investigate the outage probability and the outage capacity of the proposed network over independent Rayleigh slow fading channels. Closed-form expressions of the outage probabilities are derived for both users. Approximate outage capacity of the users are also investigated at high signal to noise ratio regime. It has been shown that the proposed cooperative NOMA can achieve superior performance compared to the non-cooperative NOMA in terms of outage probability. The tightness between the simulation and theoretical results confirms the efficiency of the proposed protocol. 相似文献
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In this paper, we propose a novel cooperative relaying scheme with multiple relays for frequency selective wireless environment. In our proposed scheme, the frequency selective wireless channel is divided into flat fading sub‐channels. Cooperative relaying is then employed over each sub‐channel to improve the system diversity order. We then investigate the asymptotic behavior of the outage probability and show that the proposed scheme achieves full diversity order in both amplify and forward (AF) and adaptive decode and forward (ADF) relaying scenarios. Furthermore, we propose a power allocation strategy to minimize the system outage probability. Simulation results confirm our analysis and show that the proposed power allocation method outperforms uniform power allocation. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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在2×1（两发一收）MIMO、时间选择性衰落信道条件下,Alamouti码的最大分集增益近似为2。为提高分集增益、增强抗信道衰落能力,提出一种适用于时间选择性衰落信道的全速率空时码（STC-TS,Space-time Code for Time-selective Fading）,通过延长发送时间,提高了信道快速变化条件下的分集增益。分析了高分集增益时编码矩阵中参数应满足的约束条件,并以＂成对错误概率上界最小＂为目标对编码矩阵进行了参数优化。仿真结果表明,当信道衰落速度足够快时,STC-TS编码获得了更多分集增益,进一步提高了传输的可靠性。 相似文献
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Full duplex (FD) technique has evolved as a viable solution to address the spectrum scarce issue. It has gained research interest for its potential to double the wireless link capacity and enhance spectral efficiency (SE). In this paper, the end-to-end performance of an amplify-and-forward full duplex relay(FDR) in asymmetric Rayleigh–Rician fading channels is explored, unlike the other works that assume symmetric fading conditions in both the links. The asymmetric or mixed fading channels properly model the realistic communication scenarios like satellite/terrestrial wireless communication systems. In this work, we consider that the source-relay link experiences Rayleigh fading and the relay-destination link experiences Rician fading. The novel exact and lower bound closed form analytical expressions for outage probability (OP) and bit error rate (BER) for the considered FD system are derived. Moreover, the effect of severity of fading and the amount of residual self-interference (RSI) on the performance of FDR are also studied. In addition, MC simulations are carried out to validate the results. It is observed that the performance metrics, OP and BER, are highly dependent on the severity of fading and the amount of RSI. Furthermore, it is found that typically at the SNR of 10 dB, an improvement of approximately 27.6% in OP is obtained. Also, our work offers appreciable SNR gain, for example, for a BER of 10−2, an SNR improvement of around 11 dB is achieved. These findings have been compared with the mixed Rayleigh–Rician fading channel conditions considering only half duplex(HD) mode. These parameter metrics are helpful in analyzing the performance of FD in various communication scenarios such as LoS/NLoS conditions and hence pave the way for more realistic FDR. 相似文献
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基于网络编码的分布式天线系统性能分析 总被引：2，自引：0，他引：2
文章针对多输入多输出（MIMO）系统在移动终端实现上的限制,提出分布式天线系统（DAS）的解决方案来获得空间分集增益。采用DAS模型,通过使用一个具有网络编码解码运算能力的辅助天线增强用户与基站间的通信,探讨基于网络编码的天线分集增益。分析比较无辅助天线系统、简单DAS和基于网络编码的DAS中断概率性能后,理论分析和计算机仿真结果表明,相比简单DAS,基于网络编码的DAS节约硬件成本并提高了频谱利用率;系统中断概率平均降低0．0164,可获得更大的分集增益。 相似文献
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Sanjeet Kumar Bhagat Dharmendra Dixit Pravas Ranjan Sahu 《International Journal of Communication Systems》2023,36(16):e5580
In this article, the performance of a wireless communication system with an intelligent reflecting surface (IRS) panel installed between the transmitter and receiver is studied. The channel is considered to be the Hoyt faded and additive white Gaussian noise. Closed-form expressions for average bit error probability (ABEP) for both coherent Gray-coded rectangular quadrature amplitude modulation and non-coherent modulation schemes are presented. We apply the moment-generating function-based method for the derivation. In addition, asymptotic ABEP expressions are also obtained. Using asymptotic ABEP expressions, we obtained diversity order which is a function of the number of IRS elements. The effect of the number of IRS elements and fading parameters on the ABEP is studied. The ABEP performance improves with an increase in the number of reflecting elements but degrades with an increase in the fading severity. The accuracy of each analytical ABEP expression is verified by the simulation of the system considered herewith. 相似文献
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The performance of multi-antenna multi- relay cooperative system is investigated in this paper. Two relaying strategies, i.e., reactive and proactive strategies are analyzed with the Amplifyand- Forward (AF) and Decode-and-Forward (DF) protocols. We derive the Cumulative Distribution Function (CDF) of the received Signal-to-Noise Ratio (SNR) at the destination, which is used to calculate the exact outage probability, for both AF and DF protocols. According to these results, we conclude that a cooperative network which composes K relays each equipped with nr antennas can achieve maximal order-(2nrK+1) diversity gain, by proper processing at relays and destination. Furthermore, the performance comparison is given, in terms of outage probability. These two strategies outperform each other in different scenarios in AF protocol, whilst proactive strategy is always better than its counterpart in DF protocol. According to these results, the optimal power allocation schemes among relay nodes are also presented, with reasonable power constraint. 相似文献
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Cooperative diversity systems have recently been proposed as a way to form virtual antenna schemes without utilizing collocated multiple antennas. In this paper, we consider the Nth best opportunistic amplify‐and‐forward (AF) cooperative diversity systems. The AF type can be regarded as one on the basis of modified channel state information. Wireless channels between any pair of nodes (i.e., direct and dual hop links) are assumed quasi‐static independent and nonidentically distributed (INID) Rayleigh fading. The best opportunistic AF (OAF) scheme requires two phases of transmission. During the first phase, the source node transmits a signal to all relays and the destination. In the second phase, the best relay is only selected on the basis of highest signal‐to‐noise ratio (SNR) scheme to forward the source signal to the destination. Therefore, the indirect link (i.e., source‐selected relay destination) can give the highest received SNR. However, the best relay selection cannot be available so that we might choose the second, third, or generally the Nth best relay. In this paper, we derive the approximated outage probability and channel capacity for the Nth best OAF relay systems over INID Rayleigh fading channels. At first, the indirect link's received SNR is approximated as harmonic mean upper bound. With this information, we obtain the given relay's Nth best selection probability as the closed form. Finally, both outage probability and channel capacity are derived as the closed forms. Simulation results are finally presented to validate the analysis. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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线性正交分集变换（ＬＤＲＴ）是近来提出的一种有效的抗衰落技术,本文对线性分集变换在莱斯衰落信道中的性能进行了分析研究,当信号调制选用ＱＰＳＫ时,计算机仿真结果：在误码率为１０＾－４条件下,信道参数Ｋ等于０ｄＢ时,ＬＤＲＴ处理增中达２１ｄＢ;随着Ｋ的增大,相应的处理增益减小,当Ｋ＝１０ｄＢ时,经过ＬＤＲＴ后的性能对高斯信道的性能只相关１ｄＢ,另外对分集矩阵的阶数Ｌ对系统误比特性能的影响进行了分析讨论 相似文献
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Shuo Liu Xuegui Song Julian Cheng Norman C. Beaulieu 《Wireless Communications and Mobile Computing》2015,15(5):812-822
Closed‐form asymptotic expressions for bit error rate and outage probability are derived for multi‐branch equal gain combining and selection combining receiver diversity over equally correlated Rician channels. Numerical results indicate that these analytical solutions can provide accurate estimation of bit error rate and outage probability in large signal‐to‐noise ratio regimes. The analytical results reveal some important insights into the performance characteristics of equal gain combining and selection combining diversity operating over equally correlated Rician fading channels. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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Nguyen Van Vinh; 《International Journal of Communication Systems》2024,37(7):e5734
It has been confirmed that the aerial intelligent reflecting surface (AIRS) can dramatically improve the coverage and quality of service of wireless communication systems. This paper proposes to exploit an AIRS to enhance the physical layer security (PLS) of wireless communication systems. In particular, the AIRS flies at convenient positions for enhancing legitimate channel gain and reducing eavesdropping channel gain. Moreover, the worst-case security is determined where the legitimate user is affected by hardware impairments (HIs) while the eavesdropper hardware is ideal (ID). The analytical expression of secrecy outage probability (SOP) of the considered systems (referred to as the AIRS-HI systems) is derived over realistic Nakagami-m channels recommended for application in the fifth and beyond generations (5G & B5G). To clarify the behaviors of the considered systems, the asymptotic expressions of signal-to-distortion-plus-noise ratio (SDNR) at the legitimate user, signal-to-noise ratio (SNR) at the eavesdropper, and SOP are also provided. Monte-Carlo simulations are employed to confirm the accuracy of the derived theorem. Numerical results confirm that the SOP of the AIRS-HI systems is dramatically higher than the SOP of the AIRS-ID systems. In other words, a strong effect of HIs on the SOP of the AIRS-HI systems is clearly indicated. Consequently, utilizing the high transmit power is not an effective solution to improve the secrecy performance of the AIRS-HI systems. In contrast, it is essential to employ an appropriate transmit power tailored to the specific system parameters. Furthermore, the considerable advantages of incorporating AIRS are demonstrated through a comparison between the SOPs of AIRS-HI systems and HI systems lacking AIRS. Additionally, a comprehensive examination of AIRS-HI system behaviors is conducted by varying various system parameters, including the predefined secrecy rate, HI level, the number of reflecting elements (REs) in AIRS, WiFi network frequency, AIRS altitude, bandwidth, and channel fading order. These observations lead to the identification of numerous recommended solutions for enhancing the SOP performance of the considered AIRS-HI systems. 相似文献
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针对相关衰落MIMO信道下的联合天线子集选择,提出了2种选择算法。首先,在已知精确信道知识的情况下,选择算法选择以使接收数据流的SNR最大化和瞬时误差概率即误符号率最小化的天线子集,从而得到平均SNR增益改善的解析表达式;其次,当信道迅速变化时,在已知信道统计知识的情况下,选择算法选择以使全部可能信道实现的平均误差概率最小化的天线子集,从而得到编码增益,在极端相关信道条件下,也可以得到分集增益;基于2种选择算法的性能分析和仿真结果验证了本文提出算法的有效性。 相似文献
